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In fairness to all, we don't discuss pricing on the Wall. Thanks for your cooperation.

To answer Ivans post because it fit right in. His question was direct pipe or pri/sec and he wanted to run a 30.

I think we got off kilter and I apologize to Ivan. Still sticking to my guns though. I think the 30 on a TT is the sweet spot. It's that on board pump that might not allow it. Did you guys know TT offers the PT110 in Canada without a on board pump? Found that interesting.

Paul I was trying to get JD not to change his secondary side pump but his primary pump to shrink that primary flow rate down from 7.1gpm. Would help in his short cycles and he would still stay in condensing mode all the time even with a small need to increase his max supply water temp. ..

"The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."

No matter how you cut it....everything is predicated on the emitters ability to disperse btus. If only half the btus go out to the secondary the return mix is that much cooler. Again, I understand what you are saying, and your reasoning, but I believe there's an application for both strategies.Both could be right, or wrong if mis-applied.

"Paul I was trying to get JD not to change his secondary side pump but

his primary pump to shrink that primary flow rate down from 7.1gpm.

Would help in his short cycles and he would still stay in condensing

mode all the time even with a small need to increase his max supply

water temp. .."

Right. And Chris will not get me to change that pump until he can explain that pumping less heat out of the boiler will reduce the cycling rate, if that is what he was talking about all this time*. Because if I slow down the boiler pump, the heat will stay in the boiler, where if I leave it alone it will go up to the twin Ts and go right back into the boiler. How will that change the cycling rate?

The cycling rate is high because the firing rate is too high because the boiler is too big for the heating zone in question, so the heat into the system is greater than the heat rejected by the system into the load. So the only ways to lower the cycling rate are to lower the heat into the boiler by lowering the firing rate, or to increase the heat removed from the boiler by increasing the output into the zone. Lowering the heat into the system can not be done by reducing the firing rate by modulation, since it is already at minimum when rapid cycling is taking place. It can be reduced only by turning it on and off. And the most diddling the pumps can do is lower the heat removal from the system, not increase it.

______

*It seems to me he was continually changing the subject of what he was talking about. First, he wanted me to put a deltaT pump in the system loop to increase the delta-T in the baseboards to get a lower return temperature in the system loop and, presumably to get a lower temperature in the boiler loop as well. Later he seems to have switched to puting such a pump in the boiler loop, where it seems it would make even less difference in getting more heat from the boiler into the load. All his suggestions on how to do that will reduce (sometimes only slightly) the heat removed from the system, and that will not reducing the cycling rate, only increase it..

ability to disperse btus. If only half the btus go out to the secondary

the return mix is that much cooler."

But is it that much cooler? And even if it were, it is still the BTUs, not the temperature, that matters. If only half the BTUs go to the emitters than are going currently, does the return from the emitters drop enough? Clearly not, since less heat is leaving the system than before. The heat that did not go up to the emitters did not disappear. It went "backwards" through the twin Ts and were mixed together and fed into the boiler. So actually more heat was going back into the boiler rather than less.

Now if I reduce the flow through the boiler circulator, the mixing takes place in the boiler instead of the return T, but that does not make any difference.

The bottom line is your boiler is to big for the heat loss, and connected load. No matter what technological bandaid (circulator) you think may fix it. It is still a boiler to big for the load. I think Hot Rod was kinda leaning in that direction many posts ago. Chris has been trying to point that out.

With all the new tools coming out for the tool box you still have to know when, and where to use it, and whether, or not its justified.

A boiler pump flowing 7 GPM to the closely spaced tees and if anything less then 7gpm is being taken by the secondary the left over goes to the boiler return tee. So my return temp is warmer not cooler.

I am moving 7gpm of 130 Degree Water out to the secondary. The Secondary takes 2 around the distribution system. The 5 left over had to go some where?

I used 125 based on what JD see's on his system side. So he has a 1 Degree Temp Difference between his boilers supply and return. Thus why he short cycles so often. So the boiler is almost in thermal equilibrium.. Basically almost no net gain or loss of heat.

Not an argument Paul for JD..

Post edited by Chris on April 2013

"The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."

think may fix it. It is still a boiler to big for the load. I think Hot

Rod was kinda leaning in that direction many posts ago. Chris has been

trying to point that out."

I have known that since about a year after I got that boiler; i.e., by the end of its first winter. I have even posted (not this thread) some things I have done to reduce the cycling rate to an acceptable rate, at a slight loss of efficiency.

So it that is all Chris was trying to point out, he could have done it in one sentence, without all this stuff about delta-T circulators, etc. I spent a week or more trying to understand what he was saying and whether it was about lowering return water temperatures, whether I understood hydraulic separation, and so on and so forth. I even spent some time trying to see what mental blocks I might be suffering from, calculated things from first principles. Now you tell me this was all wasted because all he was trying to tell me is that my boiler is too big, which I new years before this topic even came up?

Does not. You moved 7gpm across the primary side you only took 2 out to the distribution system. The other 5 left over has to go some where and it goes the opposite way, the return tee headed for the boiler. So you sending 5gpm of 130 degree water into the return mixing with 2gpm of system return water temp. I used 125 return because JD says it's common.

This is what I think most are missing. Just because the system return is X temp it doesn't mean that is what the boiler is seeing unless you remove the entire flow rate from the primary side into and around the system side. This is why I keep saying size boiler pumps for smaller flow rate. Your still moving the same amount of btu/hr from the primary to the secondary. You are not moving any more btu/hr with a higher flow at a smaller rise then I am with a lower flow with a higher rise. The formula of

gpm = btu/hr / delta-t x 500 tells us that.

JD case is not the norm. He is in condensing all the time because of the radiant house and that little heat loss on his 2nd floor. But look at a baseboard system that the majority of mod/cons are going in and it applies to most applications. Send me an email and I'd like to send you the excel spreadsheet. Play with it, using different flow rates and water temps for both the system side and the boiler side. You may find it very interesting.

I'm just trying to educate. I could really care less what JD does, it's his house. I like JD and think he gives good advice to the fellow home owners that come here.

"The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."

I agreed from the beginning your boiler was over sized. Was trying to give you a tool in helping minimize the short cycling. Your stuck that you need that Taco 007 as a boiler pump and you don't. Call Weil. Then again, they might not give you the right answer because you are a homeowner.

If you limit the high end modulation rate and convert that rate to btu/hr then you only need a pump to flow the gpm needed to get your new max btu/hr at a particular boiler temp rise. Problem with Weil is it's top secret stuff finding out the pressure drop in the HX. We had to go to the indirect chart in the manual to figure out the pressure drop and flow rate that the Taco 007 was doing.

The minimum flow rate should be defined better. They should list both the high and low flow rate. So the charts in the manuals should read as an example.

20 Degree Temp Rise (GPM = Btuh/hr / (Delta-T x 500)

Min Flow Rate Low Fire 1.7GPM ( 1.7 x 20 x 500 = 17,000 Btu/hr)

Min Flow Rate High Fire 7.1GPM ( 7.1 x 20 x 500 = 71,000 Btu/hr)

*If system flow rate exceeds 1.7gpm boiler must be piped in a primary secondary piping arrangement.

What if I don't need 71,000 Btu/hr and I want to cap it at 50%. If 0 is off then 17K is 24% modulation so 35,500 btu/hr would be 50%. Why can't I have a boiler pump that only moves 3.5gpm. That flow rate would meet both my min and my new max. This would def help you with that radiant zone if you could limit the high end of the modulation rate.

Just giving you some advice that you should take in and look at. Heck you have all summer to think about it and gather more information in making any decision if you even want to make one.

You system is unique and not one that most installers are coming up against in the majority of applications. Most mod/cons are being installed in baseboard systems and having a smaller boiler flow rate does make a difference in the boilers return water temp.

Post edited by Chris on April 2013

"The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."

I was up at 4:00 A.M this morning drinking my coffee and reading the wall until 9:00 A.M.

I spent most of the day down in the basement running new copper for our domestic water supply. I have a Triangle Tube Solo 110 down in the basement sitting on a temporary wall. I wanted to get it down there and run gas and water in order to fire it up and run it for a bit. It had a cracked heat exchanger. I bought it used and replaced the heat exchanger. I wanted to make sure everything works, and it does. It was a gamble, but it worked out.

I have a way over-sized Slant-Fin (210,000 input) installed with a Unico hot water coil that was undersized (putting out about 60,000 btu). This was installed by a contractor who I now know was a forced air guy, and not a hydronics guy.

The Triangle Tube will eventually take the place of the Slant Fin, and the hot water coil will go away as well, replaced with cast iron radiators. I put in radiators for the first floor last October. I have radiators for the second floor sitting on the front porch. I have extensive structural repairs to make in the basement before I put the Triangle Tube in place for good. In fact, I'm going to pull the Triangle Tube out of the basement before I start repairs. I'm rehabbing an 1888 house and there is fire damage in the basement that previous homeowners did not address, so I need to run new joists and pour footings and put in new posts and beams, then I'll put the boiler in for good.

I piped the near-boiler piping primary-secondary, but keep thinking about things. And wanted to see if there is some way I can make use of the Grundfos Alpha as the boiler pump. I was wondering about some things Chris has touched on in more than one post.

I think I'll be running constant circulation with ODR. My design temp is 130 degrees. I have the third floor that will not be used very often so I would still like to consider zoning in the future.

My position is that when a mod/con is piped in a primary/secondary piping arrangement or a differential by-pass is used the primary flow rate should be sized to minimize and/or eliminate elevated boiler return water temperatures.

"The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."

My position on this changes as my understanding of what Chris is talking about changes. If I accept the one where it was said that all he was trying to tell me that my boiler was oversized, and some things I could do about it, my positions are as follows:

1.) I agree that it is oversized.

2.) Since I cannot lower the firing rate below 16,000 BTU/hour without cycling, and since I did not want it cycling 12 cycles per hour, or whatever it was, I made several changes.

i.) I raised the minimum supply temperature from 85F (or whatever it was) to 110F. This increased the amount of heat rejected from the system into that heating zone when it was running, slightly decreasing the cycling rate.

ii.) I increased the boiler differential from 10F (default) to 15F, and that reduced the cycling rate some more.

iii.) I reduced the maximum firing rate when the boiler was driving this zone from 94% to 55%. By itself, this would not matter much, but at start up it helped a lot because the delay through the feedback loop was so long. Before I did that, the boiler would initially fire at 50% (I cannot change that), and it would then run up to maximum firing and rush to the upper limit before the control could lower the firing rate. By limiting maximum firing rate to 55%, boiler temperature went up slowly enough that the feedback of the controller could catch up and lower the firing rate to minimum. This further lowered the cycling rate. It is now between 5 and 6 cycles per hour (depending on outdoor temperature) that I decided was good enough.

I had done all this by a couple of years ago.

2.) We then spent a lot of time confusing one another about what Chris was talking about. Was he trying to help me get more heat out of the emitters by increasing the delta T? I though he was even though doing that would reduce the heat out of the emitters.

3.) We then confused ourselves about getting better heat transfer through the boiler, also by increasing the delta T there, which would also actually reduce the transfer rate and efficiency.

4.) Now we are just trying to reduce the return water temperature by lowering the flow through the boiler, and I do not think that is correct either. All the heat that is produced in the boiler either

i.) stays in the boiler if the boiler pump runs too slowly - \

ii.) Goes out of the boiler to the hydraulic separator and back to the boiler right away, or goes to the emitters. The heat that does not go to the emitters returns directly through the separator to the boiler. This is equivalent to 1.

iii.) The heat to the emitters is either delivered to the zone or returned to the hydraulic separator, added to the water going staight from the boiler, and sent back to the boiler, so this, too, is equivalent to 1.

iv.) Therefore the cycling rate is going to be determined exclusively by the amount of heat rejected by the emitters.

v.) Therefore, the only way left to decrease the cycling rate is to increase the heat rejected by the emitters. How is this to be done? One way it is not to be done is to reduce the flow to the emitters in order to increase the delta T up there, because that will reduce the heat rejected, not increase it, because the average temperature of the emitter will be lowered.

I think this in what my position is, now that I think I understand Crhis's position. But I am not all that sure I do understand his position.

In this case. JD system is not typical. I wouldn't be running a 5 delta-t nor would I be moving 2gpm. His system fix is a little more then just the boiler pump. How about capping off the high end modulation rate to 50% which is 35K btu/hr. Now I need a pump moving 3.5gpm. His total heat loss is, I think 32K. Run the radiant which I think he said is 25K at design. 25,000/ (10 x 500) = 5gpm. Oh no..Too much flow on the secondary side. We have a formula for that to. He would need 140 degree supply water temp at design but his boiler return would still be 130 and he still would be condensing.

You decreased the modulation rate so YOU NO LONGER NEED A BOILER PUMP MOVING 7.1 GPM. The pump only needs to move the flow require to move out the btu/hr the boiler created at your new HIGH FIRE...Which is about 3.5gpm. If we could figure out the head of that HX at 3.5gpm you could install a smaller boiler pump thus removing the flow of boiler supply and btu/hr running to that boiler return. That's been my whole entire point. When you did what you did a few years ago you where on the right track you just didn't finish the job.

Once you reduce that flow you will need to boost that water temp up to probably 140 and widen you system delta-t to 10 at design but you still will be condensing. The wear and tear of the short cycling in the end will cost you more then the pea of fuel savings if any by running a 140 supply instead of a 130 at design.

Post edited by Chris on April 2013

"The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."

I like the idea of synchronizing the hydraulics. If I could get a delta 0 pump I'd put the sensors across primary output and secondary input, with the pump itself working in perhaps the secondary loop.

To the dark side? Took you long enough. I like the term synchronizing because that is exactly what I'm trying to do. Sync the secondary flow to pull all the primary flow leaving as little or nothing of the primary flow to head right to that boiler return. Nice word use Eastman.

"The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."

Would be interested in that crack HX. Any ideas as to the cause. I'd like to apologize for high jacking your thread. Tried to answer your question and then got a little side tracked although it does pertain to what you were originally asking about.

"The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."

From my point of view, you just changed "the whole entire point" again. I continue to assume you are doing all this in good faith, and that your perception is that you have held the same point throughout. We are clearly still not talking about the same things. The longer this goes on, the more you seem to me to be changing the point and it is tough for me to keep up with you.

"You decreased the modulation rate so YOU NO LONGER NEED A BOILER PUMP

MOVING 7.1 GPM. The pump only needs to move the flow require to move out

the btu/hr the boiler created at your new HIGH FIRE...Which is about

3.5gpm. If we could figure out the head of that HX at 3.5gpm you could

install a smaller boiler pump thus removing the flow of boiler supply

and btu/hr running to that boiler return. That's been my whole entire

point. When you did what you did a few years ago you where on the right

track you just didn't finish the job."

I cannot safely reduce the flow of the boiler circulator because I reduced the maximum firing rate (not the modulation rate; to me modulation is changing the firing rate; so modulation rate might mean the rate at which the firing rate can be changed, and in a PID system, this is difficult to specify in a single number, you need at least two numbers, such as gain and damping ratio, for example) from 94% to 55% ONLY when the boiler was heating that little zone. When I run just the slab zone, that takes at least 4x more heat than the baseboard zone, the maximum firing rate is now set at 90%, and when running the indirect, it is still at 94%. I guess the indirect is a red herring since when that is running, the boiler pump is off, and the indirect's 007-IFC is on.

If I concede that when running the small zone, that a slower boiler pump might suffice, I still do not see why it would make any difference other than lowering my electric bill slightly. In other words, pumping 3.5 gpm from the boiler and leaving the heat of the other 3.6 gpm in the boiler is different from pumping 7.1 gpm from the boiler and returning 3.6 gpm to the boiler is different how? If it does not change the heat rejected by the system, how does any of that matter? You say the returned water will be cooler, and I do not see that. But even if it is as it mixes through the return T, it immediately mixes with that extra hot water in the boiler, so it is all the same as far as condensing is concerned.

It had me thinking for a while - I don't think I've heard anyone mention running the sensors for the delta on boiler and system loops, and it's certainly not in their installation manual as an application. There are a couple of issues with it, though - firstly, if you really want balanced flow, the best way to get there is to get rid of hydraulic separation. Even for imbalanced flow with a fixed degree of imbalance, a fixed bypass with a balancing valve would be the way. It seems like you're trying to use complicated controls to do something very simple. The whole point of hydraulic separation is to NOT couple boiler flow to system flow.

Secondly, there's an issue with system feedback. You want the circ to respond to greater system demand by increasing the flow. What will actually happen is that, as zones open, you will get cooler return and more flow in the system loop at the same circulator duty point. Assuming that the boiler is good at maintaining its supply setpoint, this will now result in the boiler supply being mixed down some with system return, which your control algorithm would interpret as excess system flow and turn down its duty point until system supply is once again equal to boiler supply - but now at a lower flow. So the response would seem to be the opposite of what's required.